The present invention relates to oil well servicing and in particular to a method and apparatus for the removal of paraffin build up from the inside of an oil well.
Almost every working oil well experiences problems with paraffin build up on the inside of the production tubing. This build up may occur on the inside surface of the production tubing or also on the sucker rod which reciprocates within the tubing. This paraffin build up forms a restriction in the tubing and reduces the productivity of the oil well. Consequently, almost every oil well must be periodically serviced to remove the paraffin build up in order to permit the free flow of oil through the production tubing.
Heretofore, various methods of removing paraffin build up from oil wells have been employed. In some wells, the production tubing must be removed from the casing and each individual section checked for paraffin build up while the tubing is above ground. This method requires that a portable rig be transported to the oil well site and erected in order to pull the production tubing string. This process is very expensive and requires that the oil well be shut down for considerable lengths of time in order to pull, clean and replace the production tubing.
Another method used for paraffin removal has been to heat some type of fuel above the ground surface and then pump the hot fuel down into the oil well. The heated fuel heats the production tubing and melts any paraffin build up along its length. This method is very dangerous in that the fuel must often be heated to temperatures as high as 200.degree. F., and when so heated is subject to many accidents such as accidental releases or fires that result in great injury or loss of life.
A third method attempted in the past has been to place a resistance heating element down in the oil well casing an an attempt to heat the tubing string and the oil flowing therein. Many such attempts have been unsuccessful since these heaters have been used to resistance heat the oil tubing from the outside in as well as the oil flowing therethrough. If the convection produced by the moving oil does not prevent the tubing from reaching the proper temperature, this resistance heating along major portions of the production tubing string requires very large amounts of energy. These large energy demands are very costly and often difficult to produce at a working oil well site.